Combining continuous time and discrete time signal processing in a delta-sigma modulator
AssigneeCrystal Semiconductor Corporation
InventorsNavdeep S. Sooch, Donald A. Kerth, Bruce P. Del Signore, Eric J. Swanson
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Abstract
An oversampling analog-to-digital modulator includes an analog loop filter which has a first integrator stage which operates as a continuous time integrator. the second, third, and fourth integrator stages are discrete time or sampling integrators. The continuous time first integrator provides the required thermal noise characteristics of the loop filter while the discrete time integrator stages provide loop stability and transfer characteristics which are advantageous to the overall operation of the analog-to-digital modulator.
Claims14
A plurality of serially coupled filter sections in an analog-to-digital modulator characterized in that at least one of said filter sections is a continuous time filter section and at least another of said filter sections is a discrete time analog filter section.
An analog-to-digital modulator including a summing circuit coupled to an analog loop filter which in turn is coupled to a quantizer, the output of which is coupled to a D/A converter, the output of which is coupled to one input of said summing circuit, the other input being an analog input signal, wherein said analog loop filter comprises a plurality of filter sections, at least one of said filter sections is a continuous time filter section and at least another of said filter sections is a discrete time filter section.
An analog loop filter in a delta-sigma modulator comprising a plurality of serially coupled integrator stages in which at least one of said integrator stages includes a continuous time integrator and at least another of said integrator stages includes a discrete time integrator.
An analog-to-digital modulator comprising:
- a) an input terminal for receiving an analog input voltage;
- b) an input resistor coupled to said input terminal and to a summing node;
- c) a current resistor coupled between said summing node and a voltage reference to form a current source path to said summing node;
- d) a continuous time integrator having its input coupled to said summing node;
- e) a plurality of discrete time integrator stages connected in series, said plurality having an input coupled to the output of said continuous time integrator and including at least one feedback path within said plurality of discrete time integrators;
- f) a plurality of feedforward elements each coupled to different nodes within said plurality of discrete time integrator stages;
- and
- g) a one bit analog-to-digital converter for receiving the outputs of said plurality of feedforward elements and for providing a digital output of the analog-to-digital modulator, said analog-to-digital converter output also being used to switch a current sink path coupled to said summing node, said current switch being responsive to the digital state of the output of said analog-to-digital modulator.
An analog loop filter comprising a plurality of intercoupled integrator stages in which at least one of said integrator stages includes a continuous time integrator and at least another of said integrator stages includes a discrete time integrator.
An analog loop filter comprising a plurality of integrator stages coupled in a predetermined manner in which at least one of said integrator stages includes a continuous time integrator and at least another of said integrator stages includes a discrete time integrator.
Dependencies are inferred from the claim text.